Unit testing logic in controller OnActionExecuting event - asp.net-mvc

Question

There is a custom logic to set the page title in my controller's OnActionExecuting event which sets default value for title if it is not set using an attribute on action methods:
[PageTitle("Overriden page title")]
public ActionResult About()
{
return View();
}
public ActionResult Error()
{
return View();
}
protected override void OnActionExecuting(ActionExecutingContext filterContext)
{
//Page title
var title = filterContext.ActionDescriptor.GetCustomAttributes(typeof(PageTitleAttribute), false);
if (title.Length == 1)
ViewBag.Title = ((PageTitleAttribute)(title[0])).Parameter;
else
ViewBag.Title = "Default Website Title";
}
How can I unit test this functionality?

Answer 1

This is what I ended up doing (might be helpful for anyone facing similar problem).
1) I split up the code in the controller to below:
public class BaseController : Controller
{
protected override void OnActionExecuting(ActionExecutingContext filterContext)
{
SetupMetadata(filterContext);
base.OnActionExecuting(filterContext);
}
public virtual void SetupMetadata(ActionExecutingContext filterContext)
{
//Page title
var title = filterContext.ActionDescriptor.GetCustomAttributes(typeof(PageTitleAttribute), false);
if (title.Length == 1)
ViewBag.Title = ((PageTitleAttribute)(title[0])).Parameter;
else
ViewBag.Title = "Default Page Title";
}
}
2) Deriving my HomeController from the basecontroller.
3) And then unit tested it using:
[TestClass]
public class BaseControllerTests
{
[TestMethod]
public void OnActionExecuting_should_return_attribute_value_when_set()
{
var ctx = new Mock<ActionExecutingContext>();
var controller = new HomeController();
ctx.Setup(c => c.Controller).Returns(controller);
ctx.Setup(c => c.ActionDescriptor.GetCustomAttributes(typeof(PageTitleAttribute), false)).Returns(new object[] { new PageTitleAttribute("Overriden Title") });
controller.SetupMetadata(ctx.Object);
Assert.AreEqual("Overriden Title", controller.ViewBag.Title);
}
[TestMethod]
public void OnActionExecuting_should_return_default_attribute_values_if_attributes_are_missing()
{
var ctx = new Mock<ActionExecutingContext>();
var controller = new HomeController();
ctx.Setup(c => c.Controller).Returns(controller);
ctx.Setup(c => c.ActionDescriptor.GetCustomAttributes(typeof(PageTitleAttribute), false)).Returns(new object[0]);
controller.SetupMetadata(ctx.Object);
Assert.AreEqual("Default Page Title", controller.ViewBag.Title);
}
}